The present invention generally relates to a swaging device and more specifically relates to a tool for swaging hydraulic fittings, for example, as used in the aircraft industry and the like.
Swaged fittings for use in connecting tubes, for example metallic tubes in hydraulic systems, have been used for many years. The tubes are inserted into a fitting, usually comprising a cylindrical sleeve, and then the fitting is swaged with a swaging tool to produce a fluid-tight connection between the tubes. For example, during a swaging operation, the fitting is compressed radially inwardly by the swaging tool. This causes annular ridges on an outer surface of the fitting to be flattened and transferred to an inner surface thereof. As a result, annular indentations are formed in the tube, attaching it securely to the fitting.
In certain types of swaging operations, for example, in the aircraft industry, access to the fitting to be swaged may be very limited. As a result, there has existed a need for a swaging tool that will accomplish the swaging operation, yet be compact enough to gain access to the fitting. One relatively compact swaging tool is disclosed in U.S. Pat. No. 3,848,451, herein incorporated by reference in its entirety, comprising an upper die held within a yoke and a lower die connected to the tool by a die holder. The yoke is removed by loosening a knurled nut, allowing the yoke to be separated from the remainder of the tool for initial connection to the fitting to be swaged. Despite the advances provided by this tool in terms of its relatively compact nature and versatility, there still remain situations where the ability of the tool to swage a fitting becomes very difficult and, at times, not possible.
Tubes in aircraft hydraulic systems are connected using separable and permanent type of joints. Fittings are generally made of cylindrical sleeves to receive tubes at both ends. The sleeve will be compressed externally, thereby creating radial deformation of the tubes. The pre-determined compression of fitting is done by the use of a swage tool. The fitting design makes the joint secure, fluid tight and able to withstand external environmental factors.
Early swaging tools were large and bulky and were not suitable for swaging tubes in aircraft because of the tight spacing between tubes.
The design features of a swaging tool must cater to demanding stringent aircraft assembly requirements, such as prevention of misuse, rework and must be fast and accurate. Mistakes in swaging are often extremely expensive to correct. Naturally, aircraft safety depends primarily on the performance of hydraulic systems which control the aircraft maneuvers and a faulty swage could be unsafe.
U.S. Pat. No. 5,069,058 to Hyatt, which is incorporated herein, in its entirety, by this specific reference, discloses a compact swaging tool having a removable head containing swaging dies.
Unfortunately, there are some drawbacks associated with the tool disclosed in the Hyatt patent and others similar thereto. For example, the removable connection between the die head and the cylinder is accomplished by a tongue and groove arrangement. Although this design prevents use of the tool when the tool is improperly assembled, the die head can be prone to sliding during swaging and can be unacceptably unstable in some circumstances, particularly when subjected to high stresses over an extended period of time.
There is still a need for a compact, lightweight swaging tool that is reliable even when subjected to substantial stresses during the swaging operation.
Accordingly, swaging devices are provided by the present invention for use in swaging hydraulic fittings and the like, for example to join together open ends of two tubes. The present swaging devices are strong and reliable in use and are useful for swaging those workpieces disposed in cramped quarters or difficult to access areas. The present devices are straightforward in construction and design and inexpensive to manufacture. Moreover, the present devices can be utilized with conventional, readily available swage dies.
Generally, a swaging device in accordance with the present invention generally comprises a die holder assembly and an actuator assembly. The die holder assembly includes a head, for example a substantially un-shaped head adapted to hold a first die, for example a conventional swage die, and a die block adapted to hold a second die, for example an identical second die.
The actuator assembly preferably comprises a housing, for example, a cylindrical housing, and a hydraulically operable dual piston mechanism within the housing.
The piston mechanism with the housing is adapted to move the second die toward the first die to swage a workpiece or fitting. Preferably, the pistons are separated by a sleeve member which define an upper and a lower chamber. More specifically, an upper piston having a head reciprocally retained within the upper chamber defined by the sleeve member has a rod connected to the die block. A lower piston having a head reciprocally retained within the lower chamber defined by a lower portion of the housing, has a rod slidably extending through a bore in the sleeve member and a head which abuts with a base of the sleeve member. The two pistons are biased to a retracted position, for example, by a return spring. The second piston includes an axial passageway for providing fluid communication between the upper and lower chambers when fluid is supplied to the cylinder to move the pistons and, thus, the lower die toward the upper die during the swaging operation.
The housing has a substantially closed proximal end with an exception of a fluid port defined therein, and an open distal end and sized to receive the piston mechanism during assembly.
Importantly, the swaging device of the present invention further comprises a stabilizing member (hereinafter xe2x80x9cstrut capxe2x80x9d) which is removably engaged to both the die holder assembly and the actuator assembly. More particularly, the strut cap includes a distal portion adapted to engage a proximal portion of the head, and a proximal portion adapted to engage a distal portion of the actuator assembly housing.
Preferably the strut cap is designed and adapted to control and uniformly distribute stresses, particularly principal stresses, for example compressive or longitudinal forces exerted on the device during the swaging operation. For example, the strut cap may include a pair of parallel grooves, each having a substantially uniform near circular cross section for accommodating the head. Correspondingly, the head of the die holder assembly has a proximal portion defined by two substantially parallel legs which are shaped to be received in the strut cap grooves. More specifically, these legs terminate in free ends which fit within the near circular grooves of the strut cap.
Structure is provided for facilitating proper positioning and alignment of the various components of the device, particularly for substantially preventing misalignment, for example improper assembly, between the strut cap, the head and the die holder. Such structure may include for example tabs, grooves, projections and/or recesses defined on these particular engagable components of the device. In addition, a mechanism may be provided for relieving excess pressure on the strut cap in case the device is pressurized without the head and/or die holder in place. For example, a pressure relief port may be defined within the housing.